There exist numerous mechanical devices which require simultaneous and parallel displacement of two points through the same amplitude. This applies, in particular, to top rolls in a rolling mill which must be moved parallel to themselves along fixed axes in order to take account of the thicknesses of sheet metal to be obtained and in order to ensure that said thicknesses correspond to set values. Rolls must also be capable of being tilted in order to adjust thickness or to overcome variations in thickness from one edge to another of a rolled strip. It is known that a strip which is thinner along one edge than the other by virtue of the metal being clamped more tightly at one axial end of the rolls in the mill presents a "long edge" on said side and this needs to be eliminated quickly by suitably tilting the top rolls.
These prior devices are essentially of two types, namely: hydraulic systems of the actuator type with hydraulic chambers being fed from servo-valves controlled by electronic servo-control circuits; or else mechanical systems (screw-and-nut systems, wheel and endless screw systems, . . . ) in which each of the systems is driven by a separate motor with the desired servo-control being obtained by an electronic system coupling the motors.
The drawbacks of such prior devices lie in their complexity, in the need for a high level of maintenance, in reliability which depends on the reliability of the electronic components, and in very high cost.
The present invention seeks to remedy these drawbacks by proposing robust mechanical equipment which is simple and which avoids the need for expensive, fragile and complex servocontrol, while nevertheless being easily controlled either manually or automatically or by a combination of both.